Artificial turf backing

ABSTRACT

Artificial turf ( 15 ) comprising a primary backing ( 16 ) having a first side ( 52 ) and a second side ( 53 ) and including a first backing layer ( 23 ), a second backing layer ( 24 ), a third backing layer ( 25 ) and a fourth backing layer ( 26 ), a plurality of fibers ( 19 ) sewn or tufted through the primary backing, and a secondary backing on the second side of the primary backing. The first layer may facilitate tufting, the second layer may facilitate dimensional stability, the third layer may facilitate tufted bind and the fourth layer may facilitate seam strength. The fibers may form upstanding ribbons ( 17 ) on the first side of the primary backing and the turf may further comprise an infill layer ( 20 ) disposed between the ribbons. The fibers may form a plurality of back stitches ( 27 ) on the second side of the primary backing and the secondary backing may cover the back stitches and lock in the fibers.

TECHNICAL FIELD

The present invention relates generally to the field of artificial turf,and more particularly to artificial turf having an improved primarybacking that includes multiple primary backing layers.

BACKGROUND ART

In the past, artificial turf has been made by tufting synthetic grassfibers through a primary backing. The primary backing has generally beenmade of a layer of polypropylene material, either woven or non-woven,through which the artificial turf fibers are tufted. Typically, afterthe artificial fibers are tufted through the primary backing, theunderside of the backing is coated with an adhesive to help secure thetufted fibers. Panels of the turf are then joined together to cover thedesired area. However, turf systems known in the prior art still haveproblems with tuft bind, do not provide certain desired dimensionalstability and biomechanical properties, and do not have long-lastingseaming strength.

Hence, it would be beneficial to have artificial turf which has aprimary backing that holds turf fibers in the transverse direction whilealso providing lateral seaming support and desired dimensional stabilityand biomechanical properties.

DISCLOSURE OF THE INVENTION

With parenthetical reference to the corresponding parts, portions orsurfaces of the disclosed embodiment, merely for the purposes ofillustration and not by way of limitation, the present inventionprovides improved artificial turf (15) comprising a primary backing (16)having a first side (52) and a second side (53) and comprising a firstbacking layer (23), a second backing layer (24), a third backing layer(25), and a fourth backing layer (26), a plurality of fibers (19) sewnthrough the primary backing, and a secondary backing on the second sideof the primary backing. The first layer may facilitate tufting, thesecond layer may facilitate dimensional stability, the third layer mayfacilitate tufted bind and the fourth layer may facilitate seamstrength. The fibers may form upstanding ribbons (17) on the first sideof the primary backing and the turf may further comprise an infill layer(20) disposed between the ribbons. The fibers may form a plurality ofback stitches (27) on the second side of the primary backing and thesecondary backing may cover the back stitches and lock in the fibers,and the secondary backing may be a urethane coating applied to thesecond side of the primary backing. The fibers may form a plurality ofrows (49) and a plurality of columns (48) of ribbons, the distancebetween each of the rows being substantially the same as the distancebetween the columns. The artificial turf may comprise a first panel (36a) and a second panel (36 b), the first panel having a first edge andthe second panel having a second edge, the first and second edges sewntogether to form a seam (40 a), and the turf may further comprise seamtape (46) covering the seam on the second side of the primary backing.

Accordingly, the general object of the present invention is to provideartificial turf in which the tufted fibers are more securely held inplace.

Another object is to provide artificial turf in which the fibers are noteasily pulled free from the primary backing.

Another object is to provide artificial turf that has a primary backingthat facilitates tuft bind.

Another object is to provide artificial turf which provides betterlateral support for seaming.

Another object is to provide artificial turf that has a primary backingthat facilitates seaming.

Another object is to provide artificial turf which has increaseddimensional stability.

Another object is to provide artificial turf having beneficialcushioning characteristics.

Another object is to provide artificial turf having beneficialfrictional characteristics.

These and other objects and advantages will become apparent from theforegoing and ongoing written specification, the drawings, and theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of the preferred embodiment.

FIG. 2 is an enlarged detailed view of a portion of the embodiment shownin FIG. 1.

FIG. 3 is a bottom exploded view of a portion of the embodiment shown inFIG. 1, showing the construction of the primary and secondary backing.

FIG. 4 is schematic of the four component layers to the primary backingof the embodiment shown in FIG. 1, showing the weave of each layer.

FIG. 5 is a cross-sectional view of a first alternate embodiment.

FIG. 6 is an enlarged detailed view of a portion of the embodiment shownin FIG. 5.

FIG. 7 is a cross-sectional view of a second alternate embodiment.

FIG. 8 is an enlarged detailed view of a portion of the embodiment shownin FIG. 7.

FIG. 9 is a bottom exploded view of a portion of the embodiment shown inFIG. 7, showing the construction of the primary and secondary backing.

FIG. 10 is a cross-sectional view of a third alternate embodiment.

FIG. 11 is an enlarged detailed view of a portion of the embodimentshown in FIG. 10.

FIG. 12 is a bottom exploded view of a portion of the embodiment shownin FIG. 10, showing the construction of the primary and secondarybacking.

FIG. 13 is a schematic view of a playing field made up of panels of theembodiment shown in FIG. 5.

FIG. 14 is a cross-sectional view of a prior art seam between two priorart panels of artificial turf.

FIG. 15 is a cross-sectional view of the seam between two panels of theembodiment shown in FIG. 13, taken on line 15-15 of FIG. 13.

FIG. 16 is a bottom sectional view of the seam between two panels shownin FIG. 13.

DESCRIPTION OF THE PREFERRED EMBODIMENT

At the outset, it should be clearly understood that like referencenumerals are intended to identify the same structural elements, portionsor surfaces consistently throughout the several drawing figures, as suchelements, portions or surfaces may be further described or explained bythe entire written specification, of which this detailed description isan integral part. Unless otherwise indicated, the drawings are intendedto be read (e.g., cross-hatching, arrangement of parts, proportion,degree, etc.) together with the specification, and are to be considereda portion of the entire written description of this invention. As usedin the following description, the terms “horizontal”, “vertical”,“left”, “right”, “up” and “down”, as well as adjectival and adverbialderivatives thereof (e.g., “horizontally”, “rightwardly”, “upwardly”,etc.), simply refer to the orientation of the illustrated structure asthe particular drawing figure faces the reader. Similarly, the terms“inwardly” and “outwardly” generally refer to the orientation of asurface relative to its axis of elongation, or axis of rotation, asappropriate.

Referring now to the drawings and, more particularly, to FIG. 1 thereof,this invention provides an improved artificial turf system, thepresently preferred embodiment of which is generally indicated at 15.Turf system 15 is shown as broadly including a base layer 22, asecondary backing 18, a primary backing 16, fibers 19, and an infilllayer 20.

Turf fibers 19 are sewn or tufted through primary backing 16 such thatribbons 17 extend up from primary backing 16 and are designed toresemble grass. Where they are tufted through primary backing 16, turffibers 19 form a plurality of back stitches 27 on the bottom side ofprimary backing 16. As shown in FIG. 3, turf fibers 19 are sewn ortufted through primary backing 16 in spaced rows 49 and columns 48 toform a grid of fibers 19. In the preferred embodiment, the distance 51between rows 49 and the distance 50 between columns 48 is aboutthree-eighths of an inch (″⅜). Thus, the spacing between the rows andcolumns of ribbons 17 on the top side of primary backing 16 is about thesame. Having rows 49 and columns 48 equally spaced apart allows for amore consistent playing surface laterally and longitudinally. Turffibers 19 are made of polyethylene with a face weight of 51 ounces persquare yard.

Disposed upon the primary backing 16 and between ribbons 17 of turffibers 19 is an impregnated or infill layer 20. In this embodiment,infill layer 20 is a uniform layer of 100% rubber particles, severallyindicated at 21. The rubber particles may be ambient ground rubber orcryogenically processed rubber.

Primary backing 16 is evenly covered on its underside with a continuoussecondary backing 18, which in the preferred embodiment is an urethanecoating that helps secure the tufted fibers in place. Alternatively, alatex coating maybe used. Secondary backing 18 is applied to cover theentire underside of primary backing 16. Where drainage is required,primary backing 16 and secondary backing 18 are pierced onfour-by-three-inch centers to form discrete holes of approximately 0.375inches or less in diameter.

Turf system 15 is installed by unrolling the primary and secondarybackings 16 and 18, with fibers 19 tufted in place, over base layer 22.Thereafter, infill layer 20 is spread on the top surface of primarybacking 16 and is raked into and between ribbons 17 of fibers 19 untilonly a portion of the ends of ribbons 17 are showing.

As shown in FIGS. 2-3, primary backing 16 is formed from four distinctand stacked layers 23-26. Primary backing 16 is the material throughwhich ribbons 19 are inserted. Secondary backing 18 is applied to thebottom surface of layer 26 and does not have ribbons 19 passing throughit.

First layer 23 is a conventional woven, 11 pick plain weave that iscommonly used in artificial turf. Layer 23 facilitates the tuftingprocess and provides a matrix for tufting. In the preferred embodiment,layer 23 is 100% polypropylene with a weight of 3.05 oz./yd.². ThePolyBac® style 2201 material manufactured by BP Carpet Backings, of 835Shugart Rd., Dalton Ga. 30720, may be employed in the preferredembodiment.

Second layer 24 acts to provide dimensional stability by aiding inkeeping primary backing 16 from contracting, expanding, stretching orelongating. Second layer 24 is less stretchable. Second layer 24 alsoacts to disperse impact energy over a surface area as great as threetimes the actual contact area, which results in less impact on andgreater cushioning for players using the turf. In the preferredembodiment, second layer 24 is a spunlaid, nonwoven, thermally bondedfabric made from bi-component filaments having a polyester core and anylon skin. The Colback® fabric manufactured by Colbond Inc. of P.O. Box1057, Sand Hill Road, Enka, N.C. 28728, may be employed in the preferredembodiment.

Third layer 25 is a woven, 15 pick plain weave. Layer 25 assists inholding turf fibers 19 in place where fibers 19 extend through thirdlayer 25. Layer 25 has numerous strands which provide frictional contactwith turf fibers 19, thereby helping to hold fibers 19 in place. As aresult of this layer, turf system 15 has improved bindingcharacteristics and is less likely to experience premature fiber loss.It has been found that the use of third layer 24 increases the tuft bindof the system from nine to thirteen pound pull strength. Pull strengthis the strength required to pull a turf fiber 19 from the primarybacking 16. In the preferred embodiment, layer 25 is a 100%polypropylene substrate having a weight of 3.6 oz./yd.² with apolypropylene face fiber having a weight of 1.0 oz./yd.². The FLW® style2473 manufactured by BP Carpet Backings, of 835 Shugart Rd., Dalton Ga.30720, may be employed in the preferred embodiment.

Fourth layer 26 is a woven, 9 pick leno weave that assists ininterlocking pieces or panels 36 a-w of the turf together. Layer 26assists in increasing the seam strength when panels of artificial turf15 are sewn together to cover a large surface area 38. Fourth layer 26acts as a web and provides a lateral grid across the surface, linkingthe edges of the panel of turf with the interior such that when panelsare sewn together the seam is held from pulling free at the edges of thepanel by the strength of layer 26. This creates a tight seam betweenadjacent portions of the turf field and reduces seam failure. In thepreferred embodiment, layer 26 comprises 100% polypropylene tape yamwarp and 100% polypropylene spun yarn fill. The ActionBac® style 3869material manufactured by BP Carpet Backings, of 835 Shugart Rd., DaltonGa. 30720, may be employed in the preferred embodiment.

FIG. 4 shows the weave structure of layers 23-26. Layers 23-26 may bebonded together and a portion of fibers 19 assist in mechanicallyholding layers 23-26 together. As shown in FIGS. 2-3, back stitches 27protrude slightly out from the bottom of fourth layer 26 and secondarybacking 42 adheres to and coats back stitches 27.

Turf fibers 19 are tufted through primary backing 16 with a conventionalthree-eights of an inch (″⅜) gauge tufting machine having certainmodifications. Fibers 19 are inserted by vertical, reciprocating needlespositioned in a row across a fifteen foot wide conventional machine.Individual cones of fiber filaments are arranged in racks on the creel.A guide is provided for each filament coming from the creel, with afilament feeding each needle on the needle bar. From the creel thefilaments pass through guides to the ribbon puller rolls of the tuftingmachine. Adjusting the speed of these puller rolls controls the amountof ribbon supplied to the machine and is a factor in determining theheight of the tufted ribbon. The filaments then pass through a series ofvertically aligned and fixed guides which direct the flow of thefilament to the jerker bar, which controls the slack caused by themovement of the needles.

The filaments are then threaded through the respective needles in theneedle bar. Each layer 23-26 of primary backing 16 into which fibers 19are inserted is supplied in roll form, located in front of the tuftingmachine. Spiked rolls positioned on the front and back sides of thetufting machine draw the four layers 23-26 over the bed plate andthrough the machine. The speed of the spike rolls controls the stitchesper inch. Moving the primary backing slowly through the machine producesmore stitches per inch while a faster rate produces few stitches perinch longitudinally. The section between the creel and the tuftingmachine is modified to provide the correct number of rolls for each ofthe layers of primary backing 16.

In order to manufacture the preferred embodiment, certain othermodifications to a conventional tufting machine were made. First, theconventional needles were placed with heavier, more rigid and moredurable needles to allow for the needles to punch through layers 23-26.The 1457 RWS needles manufactured by Eisbar, of Germany, maybe employedin the preferred embodiment. In addition, the conventional gear box wasreplaced with a more powerful exterior mounted gear box to allow for themachine to pull all four layers 23-26 under the correct tension.Finally, before the final tufting process, layers 24 and 25 are needlepunched together. This facilitates the feeding of all four layers 23-26through the tufting machine at the same time. The speed of the spikedrolls and the numbers of needles on the needle bar are modified toprovide the equal spacing between the rows and columns of ribbon 17 ofabout three-eighths of an inch (″⅜).

Located below the bed plate are the looper and knife combination for thepile cut employed in the preferred embodiment, with the lopper and knifeholding and cutting the fiber filaments in a single operation. Theloppers are of a reversed-C shape, with a cutting surface on the topinside edge of the crescent. The loppers are used in combination withknives having a ground cutting edge on one end. As primary backing 16advances through the machine toward the loopers, the fiber filamentspicked up from the needles are cut by the scissor-like action betweenthe looper and the knife.

Two biomechanical properties of the preferred embodiment were tested andmeasured: the ability of the surface to reduce impact forces associatedwith landing on the surface, also referred to as cushioning, and theability of the surface to provide frictional support at the interfacebetween a sports shoe and the surface, also referred to as traction.

These properties are relevant because excessive impact forces, fromrunning or falling, can have a negative effect on a player using theplaying surface. The frictional aspects of the surface are also relevantand generally break down into translational and rotational friction.Ideally, the friction between the turf surface and the player's athleticshoe should be at a level high enough to avoid slipping, therebyproviding for optimum performance, such as fast acceleration and quickdirectional changes, while being at a level low enough to limitinjuries.

The preferred embodiment was tested by mounting samples on a thinaluminum plate that was bolted to a force platform designed to measureand record all relevant data. Data was sampled at a frequency of 1000 Hzfor the cushioning and rotational friction tests and 100 Hz for thetranslational friction test. A workstation recorded the force data fromthe force platform and the data was analyzed using conventionalsoftware. A representative standard Adidas® Supernova running shoe and arepresentative Nike® Roma FT cleated soccer shoe were used as thesubject footwear.

Vertical drop tests were performed using masses of 4 kg and 7.3 kg. Fivetrials at heights of 5, 10 and 20 cm, respectively, were performed withboth of the masses. Peak impact forces (F_(zmax)) were recorded andaverages determined. The height and masses were chosen to simulatetypical impact forces that might occur on the sporting surface. Theimpact loading rate was calculated by dividing the peak impact force bythe time necessary to reach the peak. Table 1 shows the measured impactresults for the preferred embodiment. TABLE 1 Vertical drop test meanand standard deviation impact peak results (cushioning) from thesurface. F_(zmax)[N] Mass [kg] 4  4  4 7.3  7.3  7.3 Height [cm] 5 10 205   10   20   Trial 1 434 746 1146 673 1114 1920 Trial 2 410 768 1359596 1110 2449 Trial 3 480 627 1552 720 1158 1904 Trial 4 515 619 1080690 1080 2290 Trial 5 510 703 1151 550 1092 1998 Average 475 693 1219653 1105 2069 Std. Dev. 38 60 122 50 12 195

Table 2 shows the impact loading rates results for the preferredembodiment. TABLE 2 Vertical drop test mean and standard deviationimpact loading rate results from the surface. Max Loading Rate [kN/s]Mass [kg] 4  4  4 7.3  7.3  7.3 Height [cm] 5 10 20 5   10   20   Trial1 21.7 57.4 81.9 39.6 65.5 137.1 Trial 2 22.8 59.1 113.3 28.4 65.3 204.1Trial 3 32.0 39.2 141.1 45.0 72.4 119.0 Trial 4 36.8 41.3 83.1 38.3 67.5176.2 Trial 5 34.0 54.1 88.5 26.2 64.2 124.9 Average 29.6 50.9 95.0 35.466.1 146.1 Std. Dev. 6.0 8.5 16.1 6.1 1.2 26.8

Live impact testing was also performed on the preferred embodiment. Fivesubjects with a mean age of 22.8 years, a mean height of 1.79 meters anda mean mass of 74.4 kg, ran heal to toe style at a velocity of 4 m/s-0.4m/s with the right foot making full contact with a turf sample affixedto the force platform. Running velocity was measured. Five trials wereperformed for which impact peaks (F_(zmax)) were recorded. The impactloading rate was calculated by dividing the peak impact force by thetime necessary to reach the peak. Table 3 shows the live impact testresults. TABLE 3 Mean and standard deviation of the maximal verticalimpact forces, F_(zmax), and impact loading rates. Subject 1 2 3 4 5Force (N) Trial 1 1805 1041 1073 1218 1048 Trial 2 1632 1159 953 12251189 Trial 3 1834 1219 1049 1159 852 Trial 4 1743 1074 1428 1288 876Trial 5 1637 962 1363 1427 981 Average 1728 1091 1162 1244 1002 Std.Dev. 85 61 175 39 40 Loading Trial 1 50.1 26.0 25.5 38.1 55.2 Rate Trial2 41.8 36.2 23.8 36.0 54.0 (kN/s) Trial 3 48.3 42.0 31.8 36.2 30.4 Trial4 43.6 29.8 33.2 39.0 32.5 Trial 5 42.0 25.3 31.7 40.8 46.7 Average 44.630.7 29.7 37.8 44.4 Std. Dev. 3.3 5.2 3.6 1.4 10.9

Translational friction testing was performed using a cart consisting ofa weighted sled attached to a sport shoe. The cart was placed over thesample such that only the sole of the shoe came in contact with thesample surface and, as the cart was pulled, the shoe was dragged acrossthe surface while the force platform measured the vertical andhorizontal loads. The coefficient of friction for the surface wasdetermined from: $\begin{matrix}{\mu = \frac{F_{h}}{F_{v}}} \\{\mu = {{coefficient}\quad{of}\quad{friction}}} \\{F_{h} = {{horizontal}\quad{or}\quad{frictional}\quad{force}}} \\{F_{v} = {{vertical}\quad{or}\quad{normal}\quad{{force}.}}}\end{matrix}$

Trials were performed with a mass of 12.5 kg and the average of thedynamic frictional coefficient was calculated using the three middlevalues. The results of the test for the two subject test shoes are setforth in Tables 4 and 5, respectively. TABLE 4 Mean and standarddeviation of maximal free moment of rotation, M_(max), and translationalfriction coefficients for the Adidas Supernova running shoe. RunningShoe Trans. Friction Coeff. (u) Direction 1 Direction 2 Trial 1 0.690.94 Trial 2 0.79 0.83 Trial 3 0.82 0.81 Trial 4 0.83 0.76 Trial 5 0.800.77 Average 0.80 0.88 Std. Dev. 0.02 0.03

TABLE 5 Mean and standard deviation of maximal free moment of rotation,M_(max), and translational friction coefficients for the Nike soccershoe. Soccer Boot Trans. Friction Coeff. (u) Direction 1 Direction 2Trial 1 1.64 1.50 Trial 2 127 1.21 Trial 3 1.18 1.14 Trial 4 1.13 1.10Trial 5 1.12 1.16 Average 1.19 1.17 Std. Dev. 0.07 0.04

Rotational friction was also determined with live subjects. Each of fivesubjects stood on the ball of their right foot and made a full 180° turnon the surface. The rotational friction is directly proportional to themaximum vertical free moment of rotation (M_(max)) which was measuredusing the force platform. The vertical free moment of rotation (M_(max))was recorded for the five trials and an average of the three middletrials was calculated. High moments of rotation correspond to highresistance against rotation. The results from the tests are set forth inTable 6. TALBE 6 Rotational Friction (Nm) Subject Shoe 1 1 2 2 3 3 4 4 55 Type Running Soccer Running Soccer Running Soccer Running SoccerRunning Soccer Trial 1 22.0 32.8 26.2 29.2 18.3 23.4 32.2 41.1 16.5 18.5Trial 2 29.9 33.0 24.3 28.9 22.8 26.0 33.3 44.0 13.5 21.5 Trial 3 28.036.0 25.8 29.6 24.0 31.1 36.1 43.8 18.0 23.7 Trial 4 26.5 34.2 24.2 23.619.4 25.2 30.4 44.0 14.7 19.6 Trial 5 20.5 33.4 28.6 37.2 18.3 20.8 31.242.2 17.7 22.7 Average 25.5 33.5 25.4 29.2 20.2 24.9 32.2 43.3 16.3 21.3Std. Dev. 3.1 0.6 1.0 0.4 2.3 1.3 1.1 1.0 1.5 1.6

The above results indicated that the preferred embodiment was highlyrecommended for both cushioning and friction properties, the highestavailable ranking.

FIGS. 5-6 show an alternate embodiment 28 of the turf system shown inFIG. 1. This first alternate embodiment 28 is similar to turf system 15in all respects except that it has an infill 29. Infill 29 is made up of70% granular ambient rubber particles from recycled tires and 30% kilndried sand particles 31. Rubber 30 is washed after processing and issubstantially free of metal particles. In this embodiment, the mesh sizeof granular rubber 30 is between 8 and 16 with a specific gravity of1.13 to 1.27. Sand 31 is clean, dry, rounded silica sand and has a meshsize between 20 and 40. Infill 29 is mixed prior to application toensure consistency and uniformity.

FIGS. 7-9 show a third embodiment 32. Embodiment 32 is the same assecond embodiment 28 in all respects except that the primary backing 33does not include layer 23. Rather, as shown in FIGS. 8-9, primarybacking 33 is made up of three layers, rather than four. In particular,primary backing 33 is made up of layers 24, 25 and 26, with layer 24being the top layer, layer 25 being the middle layer, and layer 26 beingthe bottom layer. Secondary backing 18 is applied to the bottom surfaceof layer 26 as in the preferred embodiment.

FIGS. 10-12 show a fourth embodiment 34. Embodiment 34 is the same asthird embodiment 32 in all respects except that the primary backing 35is made up of two layers, rather then three layers. In particular,primary backing 35 is made up of layers 25 and 26, with layer 25 beingthe top layer and layer 26 being the bottom layer.

FIG. 13 shows panels of turf 28 arranged to provide a playing surface 38for a football field. Playing surface 38 is formed by a series oflaterally extending rectangular sections or panels 36 a-w. As shown inFIG. 13, in order to provide a uniform playing surface, each of panels36 a-w is connected to at least one adjoining panel at seams 40 a-u.

FIG. 14 shows a lapp sewn seam known in the prior art. As shown in FIG.14, in the prior art, in order to assure that stitching 43 did not pullout from the edges of the two adjoining panels, an excess portion 42 ofprimary backing 41 was left to provide support for seam 43.

In contrast, FIG. 15 shows a seam employed with turf 28. As shown,because of the additional strength and stability of primary backing 16,additional leftover backing material 42 is not needed to hold stitching45 in place. Rather, stitching 45 is looped through primary backing 16in panels 36 a and 36 b. Layer 26 has lateral strength at the edges of36 a and 36 b, respectively, so that stitching 45 does not pull out fromsuch edges. This allows the edges of primary backing 16 and secondarybacking 18 of panels 36 a and 36 b to abut directly against each other.Thus, in contrast to the prior art shown in FIG. 14, no excess materialis located between secondary backing 18 and base 22. This allows for aneat and even butt seam 40 a, which in turn provides a flatter and moreeven playing surface 38. The 81500T turf sewing machine manufactured byTextile and Industrial Sales Inc., of 404 Whitener Drive, Dalton, Ga.30722-0768, maybe used in the preferred embodiment to sew stitching 45.

FIG. 16 is a bottom view of butt seam 40 a with the addition of seamtape 46. As shown in this view, panels 36 a and 36 a abut each other atseam 40 a. Stitching 45 is used to connect the abutting edges of panels36 a and 36 b. Once loop stitching 45 has been sewn, seam tape 46 maybeapplied over the stitching to provide protection for the stitching andto add additional strength to seam 40 a. Again, as shown in FIG. 16,because excess portions of primary and secondary backing 16 and 18 arenot necessary to hold stitching 45 in place due to the strengthcharacteristics of primary backing 16, seam tape can be applied over thestitching 45 as shown. The Turf-lock seam tape manufactured byTurfstore.com Inc., of 237 Boling Industrial Way, Calhoun Ga. 30701, maybe employed in the preferred embodiment.

The present invention contemplates that many changes and modificationsmay be made. Therefore, while the presently preferred form of the turfhas been shown and described, and several modifications and alternateembodiments discussed, persons skilled in this art will readilyappreciate that various additional changes and modifications may be madewithout departing from the spirit of the invention, as defined anddifferentiated by the following claims.

1. Artificial turf comprising: a primary backing having a first side anda second side and comprising a first backing layer, a second backinglayer, a third backing layer, and a fourth backing layer; a plurality offibers sewn through said primary backing; and a secondary backing onsaid second side of said primary backing.
 2. The artificial turf setforth in claim 1, wherein said first layer facilitates tufting, saidsecond layer facilitates dimensional stability, said third layerfacilitates tuft bind and said fourth layer facilitates seam strength.3. The artificial turf set forth in claim 1, wherein said fibers formupstanding ribbons on said first side of said primary backing andfurther comprising an infill layer disposed between said ribbons.
 4. Theartificial turf set forth in claim 1, wherein said fibers form aplurality of back stitches on said second side of said primary backingand said secondary backing covers said back stitches and locks in saidfibers.
 5. The artificial turf set forth in claim 1, wherein saidsecondary backing is a urethane coating applied to said second side ofsaid primary backing.
 6. The artificial turf set forth in claim 1,wherein said fibers form a plurality of rows and columns of ribbons, thedistance between each of said rows being substantially the same as thedistance between each of said columns.
 7. The artificial turf set forthin claim 6, wherein said distance between each of said rows is about⅜inches.
 8. The artificial turf set forth in claim 1, wherein saidartificial turf comprises a first panel and a second panel, said firstpanel having a first edge and said second panel having a second edge,said first and second edges sewn together to form a seam, and furthercomprising seam tape covering said seam on said second side of saidprimary backing.
 9. The artificial turf set forth in claim 1, whereinsaid first layer comprises a polypropylene weave.
 10. The artificialturf set forth in claim 1, wherein said second layer comprises apolyester core and a nylon skin.
 11. The artificial turf set forth inclaim 1, wherein said third layer comprises a polypropylene weave. 12.The artificial turf set forth in claim 1, wherein said fourth layercomprises a polypropylene tape warp and a polypropylene spun yarn fill.